The present invention relates to a control device of a powertrain of a vehicle or the like, particularly to a control device of a powertrain with a centrifugal pendulum damper.
Conventionally, the use of an engine cylinder cut-off operation and homogenous charge-compression ignition (HCCI) combustion, and furthermore, of an art such as making an automatic transmission torque converter-less by eliminating the torque converter, are known for increasing fuel efficiency of a vehicle equipped with a powertrain comprising a power transmission path which extends from an engine to a drive wheel via an automatic transmission.
However, there is a tendency for output torque fluctuations to become larger in an engine which has adopted a cylinder cut-off operation or HCCI combustion, and also, because engine torque fluctuations are output from an automatic transmission without attenuation when the automatic transmission has been made torque converter-less, torque fluctuations transmitted to a power transmission system on an automatic transmission output side become larger in a vehicle using such an art. In particular, torsional vibrations caused by these larger torque fluctuations may become a cause of vibration or noise generation in various vehicle parts if amplified by resonance of the power transmission system.
For the sake of convenience, the term “automatic transmission” will hereinafter be described as including not only a multi-stage automatic transmission provided with a transmission mechanism for switching between gear ratios in a step-wise manner, but as also including a continuously variable automatic transmission (CVT) provided with a transmission mechanism for continuously changing gear ratios as well. Additionally, a transmission mechanism which is an automatic transmission does not include a torque converter or a torsion damping mechanism.
With respect to the above-described problem, an art is known, such as, for example, operatively coupling a centrifugal pendulum damper to a power transmission shaft as disclosed in JP2014228009A. The centrifugal pendulum damper has a support member which rotates together with a power transmission shaft, and a pendulum which is a mass supported by the support member so as to be able to swing centered on a circumferential point at a fixed radius from an axial center of the support member. When the pendulum swings due to torque fluctuations, a circumferentially-directed component of force is generated in the support member which receives the centrifugal force acting on the pendulum. This component of force acts as an anti-torque which suppresses torque fluctuations of the support member and the power transmission shaft.
In an engine low-speed rotation range, such as at a time of starting, the centrifugal pendulum damper coupled to the power transmission shaft also rotates at a low speed and the centrifugal force acting on the pendulum is reduced, and due to this reduced centrifugal force, a torque fluctuation suppression operation of the pendulum becomes unstable and the pendulum may cause generation of abnormal noise due to contact with a peripheral member. In the invention of JP2014228009A, a connection/disconnection mechanism for attenuating power transmission to the centrifugal pendulum damper is provided between the power transmission shaft and the centrifugal pendulum damper to suppress generation of abnormal noise. As described below, a connection/disconnection mechanism of the present invention is a frictionally-engaged type of clutch which transmits power by frictional force and which can smoothly transmit torque, even when there is a difference in rotational speeds between an input shaft and an output shaft, by shifting from a released state to a slip state or an engaged state while adjusting an engagement degree by controlling hydraulic pressure, electric current, or the like. In the present invention, “engaged” and “released” denote that the connection/disconnection mechanism as a whole is connected and cut-off, respectively, and “slipping” denotes an incomplete connection in which the connection/disconnection mechanism is slipping.
However, when the connection/disconnection mechanism is disposed between the power transmission shaft and the centrifugal pendulum damper as in the prior art described in JP2014228009A, an engagement degree of the connection/disconnection mechanism increases to a slip state or a fully engaged state during a gear shift control, a moment of inertia (an inertia) of the centrifugal pendulum damper is added to the power transmission shaft as a load inertia moment, and because the moment of inertia of the power transmission shaft is thus increased, the gear shift control cannot fully accommodate for this change, and there is a possibility that a gear shift duration will be lengthened. There is also a possibility of a transmission shock being generated if a moment of inertia of the power transmission shaft is increased rapidly. Note that a transmission shock is also possible in a case where the moment of inertia of the power transmission shaft is rapidly decreased when the connection/disconnection mechanism changes from the engaged state to the released state during a gear shift control.
Note that the above-described problem is not limited to a case where an engagement degree of the connection/disconnection mechanism changes during a gear shift control of the transmission mechanism but is also a problem in a case where an engagement degree changes prior to a gear shift control and the changed engagement degree starts an execution of a gear shift control.
The present invention was made in view of the above-described problems related to a control device of a powertrain with a centrifugal pendulum damper and aims to prevent a degradation of transmission performance due to a change in an engagement degree of a connection/disconnection mechanism.
In order to solve the aforementioned problem, a control device of a powertrain with a centrifugal pendulum damper according to the present invention has characteristics of being configured as follows.
According to one aspect of the present invention, a control device for a powertrain comprises a transmission control module. The powertrain comprises a power transmission shaft and a centrifugal pendulum damper. The power transmission shaft is configured to transmit power between a drive source and an automatic transmission, and the centrifugal pendulum damper is configured to be operatively coupled to the power transmission shaft and a connection/disconnection mechanism. The automatic transmission is configured with a transmission mechanism of a hydraulic pressure control type, and the transmission control module, which is operatively coupled to the transmission mechanism, is configured to perform a control to supply transmission hydraulic pressure to the transmission mechanism. The transmission control module executes a transmission characteristic changing module which is a software or firmware program that changes a control characteristic of transmission hydraulic pressure according to an engagement degree of the connection/disconnection mechanism.
According the above configuration, when the engagement degree of the connection/disconnection mechanism changes, a moment of inertia of the power transmission shaft changes according to the engagement degree, because the transmission characteristics changing processor changes the control characteristic of the transmission hydraulic pressure supplied to the transmission mechanism according to the engagement degree, a lengthening of the gear shift duration due to an increased moment of inertia and the generation of transmission shock accompanying a rapid increase or decrease in the moment of inertia can be restrained, and a reduction in transmission performance due to a change of the engagement degree of the connection/disconnection mechanism can be prevented.
Further, the transmission characteristic changing module may increase the transmission hydraulic pressure with an increase in the engagement degree of the connection/disconnection mechanism.
With the above configuration, the higher an engagement degree of the connection/disconnection mechanism is, the transmission characteristic changing module increases the transmission hydraulic pressure and therefore, for example, by increasing the transmission hydraulic pressure of engaged elements of the transmission mechanism at a time of upshifting the transmission mechanism, a lengthening of the gear shift duration can be suppressed.
Further, the transmission characteristic changing module may change the control characteristic of the transmission hydraulic pressure according to a moment of inertia of the power transmission shaft, the moment of inertia being based on the engagement degree of the connection/disconnection mechanism.
With the above configuration, the transmission characteristic changing module changes the transmission hydraulic pressure according to a moment of inertia of the power transmission shaft which changes according to the engagement degree of the connection/disconnection mechanism. Therefore, even when the engagement is changed during a gear shift control, the gear change control may be performed with a higher degree of accuracy by changing the transmission hydraulic pressure according to changes in the moment of inertia which directly influence transmission performance. Therefore, lengthening of the gear shift duration and deterioration of transmission performance due to a change in the engagement degree of the clutch mechanism can be prevented.
Further, when the engagement degree is changed during a gear shift control, the transmission characteristic changing module may change the control characteristic of the transmission hydraulic pressure according to the engagement degree after the gear shift control.
With the configuration as above, the transmission characteristic changing module changes the transmission hydraulic pressure according to an engagement degree of the connection/disconnection mechanism when the engagement degree is changed during a gear shift control during a gear shift control. Therefore, even when a gear shift control and a control requiring a change of the engagement degree of the connection/disconnection mechanism (for example, a cylinder cut-off operation) overlap, both controls may be executed properly.
Further, the transmission characteristic changing module may change the transmission hydraulic pressure in a step-up process during the gear shift control according to the engagement degree of the connection/disconnection mechanism.
With the configuration as above, the transmission characteristic changing module changes the transmission hydraulic pressure in a step-up process during a gear shift control according to the engagement degree of the connection/disconnection mechanism. Therefore, the transmission hydraulic pressure is changed from the torque phase before the inertia phase is started, and, from the beginning of the start of the inertia phase, which is directly influenced by the engagement degree, the transmission hydraulic pressure is changed to a hydraulic pressure which corresponds to the engagement degree. Therefore, since a delay does not occur in the changing of the transmission hydraulic pressure, lengthening of the gear shift duration and generation of transmission shock can be more surely prevented.
Further, the transmission characteristic changing module may determine the engagement degree of the connection/disconnection mechanism based on one of a rotational differential of the connection/disconnection mechanism and a control hydraulic pressure of the connection/disconnection mechanism.
According to the above configuration, the transmission characteristic changing module determines an engagement degree of the connection/disconnection mechanism based on a rotational differential of the connection/disconnection mechanism or a control hydraulic pressure for the connection/disconnection mechanism. Therefore, with a simple configuration equipped with only a rotational speed sensor or hydraulic pressure sensor for simply detecting a rotational differential of the connection/disconnection mechanism or for detecting a control hydraulic pressure, the advantageous effects of the above-described aspects of the invention may be realized.